1. Technical Field
The present invention relates to the apparatuses and methods in the metallurgical field, especially for electromagnetic melting and purification of aluminium, copper, brass, lead and bronze alloys prior to foreseen next treatments. These materials will be thereafter referred to as metals.
2. Prior Art
Magnetic induction crucible furnaces for heating and melting of metals by an alternate magnetic field are well-known.
The known induction furnaces permit use of solid raw material from the start-up phases, but they must be supplied by high-frequency electrical energy and special power sources are necessary for the compensation of a high reactance. The electrical effectiveness of such furnaces is consequently low.
The induction channel furnaces have a high power efficiency, but during the start-up phases they use only liquid metal to fill all the space, where a Joule heat shares out. Therefore a channel induction furnace cannot be stopped during the whole operation process. Furthermore, an induction channel furnace tends to deposit on the inner walls oxides and inter-metallic materials as an effect of the opposition to the current induced in the magnetic field of the inductor. Many cleaning methods of induction channels are not effective, are too expensive and, most important, lead to great losses because of the interruption of the main melting process.
These type of furnaces do not provide any purification of molten metal during or after melting. They do not allow discharge of the molten metal without tilting the furnace. This operation can break the refractory of the apparatus. Only the magneto-dynamic pump, described in the Patent of Prof. V. Polishchik (USSR No 176.184) permits pumping out the treated metal, but this pump had been designed like a induction channel furnace and can be polluted by the melting process of metallic alloys.
The conventional magnetic induction furnaces are not able to purify the molten metal during or after melting; therefore, purification is achieved through mechanical stirring and addition of chemical components containing thorium and chlorine, causing a further pollution of the environment.